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IMPROVEMENT, IN WOODSGRWS.

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TO ALL WHOM IT MAY CONCERN:

Be it known that I, HAYwARD A. HARVEY, of Orange, in the county of Essex, and State of New Jersey,

have invented a new and useful Improvementin Wood-Screws; and I do hereby declare that the following is aV full, clear, and-exact description thereof. Y

The nature of my invention consists in so forming the core` of a screw as to cause the upper portion of it to, present the appearance of a. series of truncated cones between the threads,one above the other, with'thcir bases toward the point, which I accomplish by so shaping and setting the chasing-toolas to cut the threads deeper on the under side than on the upper, as will be readily understood by those accustomed tothe inanuf'acture of screws. The core orrbody of the screwis thus made to operate upon the wood, into which it is inserted in the manner of a wedge, with its point toward the surface, thus imparting to the screw anl increased power of resistance to withdrawal. Moreover, in displacing the wood to make room for itself, a screw of this formcrowds the wood backward or toward the surface, thus compacti'ng it in that direction, which is obviously advantageous in increasing its holding-qualities. A

The drawings, which `accompany and form a part of this specification, embrace an enlarged external view, and a longitudinalsection of my invention, similar letters of reference being used to indicate the same parts of both figures. i

a represents the head, b the shank, c the thread, ol the core, and e the point.

Figure 2 represents a section of the screw in use, fand g being two pieces of wood joined together by it; and in speaking ofthe surface of ytne wood I refer to tfin which the head is embedded.

What I claim as my invention, and desire to secure by Letters Patent of the United States, is v A screw, constructed in the ordinary manner, with the exception that the thread is cut deeper on the under side than on the upper, substantially as and for the purpose set forth. l v

A H. HARVEY.

Witnesses:

. WM. H.`BIsHoP,

A. DE LACY. 

